Force compensating arrangement for a radial piston machine

ABSTRACT

The rotor of a radial piston pump has cylinders, and pistons cooperating with an eccentric actuating ring so that the resultant of the inward directed forces passes through the axis of the actuator ring at an angle less than 90* to a plane through the axes of the rotor and of the actuator ring. The high pressure and low pressure control ports on the control pintle supporting the rotor, are angularly displaced relative to this plane so that the resultant of outward directed pressure forces, which passes through the rotor axis, is parallel to the resultant of the inwardly directed forces, and compensates the same.

United States Patent [191 Nonnenmacher Oct. 7, 1975 FORCE COMPENSATINGARRANGEMENT FOR A RADIAL PISTON MACHINE [75] Inventor: GerhardNonnenmacher,Korntal,

211 App]. No.: 353,625

[30] Foreign Application Priority Data Apr. 22, 1972 Germany 22198813,188,918 6/1965 Bjorklund 91/497 3,192,867 7/1965 Bjorklund et a].3,408,948 11/1968 Boyd 91/498 FOREIGN PATENTS OR APPLICATIONS 775,8535/1957 United Kingdom 91/498 Primary Examiner-William L. Freeh Attorney,Agent, or FirmMichael S. Striker [57] ABSTRACT The rotor of a radialpiston pump has cylinders, and pistons cooperating with an eccentricactuating ring so that the resultant of the inward directed forcespasses through the axis of the actuator ring at an angle less than 90 toa plane through the axes of the rotor and of the actuator ring. The highpressure and low pressure control ports on the control pintle supportingthe rotor, are angularly displaced! relative to this plane so that theresultant of outward directed pressure forces, which passes through therotor axis, is parallel to the resultant of the inwardly directedforces, and compensates the same.

1 Claim, 5 Drawing Figures US. Patent Oct. 7,1975 Sheet1of3 3,910,162

U.S. Patent Oct 7,1975

Sheet 2 of 3 TI s US. Patent 0a. 7,1975 Sheet 3 of3 3,910,162

FORCE COMPENSATING ANGENIENT FOR A RADIAL PISTON MACHINE BACKGROUND OFTHE INVENTION The US. Pat. No. 3,064,583 discloses a radial piston iChine, which may operate as a pump,

machine, pump or hydraulic motor with a rotor mounted on a controlpintle having partcircular high pressure and low pressure control portscooperating during rotation with cylinder ports provided at the innerends of passages which are connected with the cylinders, respectively.In machines of this type, forces pressing the rotor on the high pressureside against the control pintle are compensated by correspondingpressure areas, but it has been found that substantial forces occur inthe direction of the eccentricity of the actuator ring, which are notcompensated. This has the result that due to the one sided forces,increased wear of the parts occurs, so that the span of life of themachine is reduced.

SUMMARY OF THE INVENTION It is an object of the invention to provide theradial piston machine in which all occurring forces are compensated sothat the operation and span of life of the machine are improved.

With this object in view, the present invention provides a radial pistonmachine in which the cylinder ports on the inner surface of the rotorare circumferentially displaced to lead the cylinders during rotationwhile the machine operates asa pump, for example, while the highpressure and low pressure control ports on the pintle are angularlydisplaced relative to a plane passing through the axes of the rotor andof the actuator ring so that the high pressure control port is movedtoward the inner dead center position of the rotor in which the rotor isclosest spaced from the actuator ring.

In such an arrangement, the inner relieving pressure area on the controlpintle is turned so that its direction conforms to the resultant of theforces acting on the bearings of the rotor.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinventionitself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic cross-sectionalview illustrating a first embodiment of the invention;

FIG. 2 is a schematic cross sectional view illustrating a secondembodiment of the invention;

FIG. 3 is partially a cross-sectional view corresponding to FIG. I, andpartially a diagram illustrating the inwardly directed forces producedby the eccentric actuator ring;

FIG. 4 is a cross-sectional view illustrating a radial piston machineaccording to the prior art; and

FIG. 5 is a cross-sectional view of the embodiment of FIG. I, andincluding a diagrammatic illustration of the compensation of theresultant of the inwardly directed mechanical forces by the resultant ofoutwardly di rected pressure forces in accordance with the invention.

DESCRIPTION OF THEPREFERRED EMBODIMENTS As shown in FIGS. 1, 3 and 5, aradial piston ma has a control pintle 10 surrounded by the innercylindrical surface 11a of a rotor 11, and supporting rotor 11 forrotation about an axis A,. A stationary actuator ring 14 has an innercylindrical surface 14a having an axis A parallel with rotor axis A andspaced therefrom the distance e representing the eccentricity of theactuator ring 14 in relation to the rotor 11.

Rotor 11 has six cylinders 15 with radial axes, not

shown, in which spherical pistons 16 are mounted for" radial movement,and abut the. inner surface 14a of the actuator ring 14. During rotationin the direction of the i arrow 0, each piston 16 passes successivelythrough i the inner dead center point Ti and the outer dead center pointTa of plane B. Rotor 11 is closer to the actuator ring 14 at the innerdead center point Ti than at the outer dead center point Ta.

The cylinders 15 do not directly communicate with the control ports 12and 13, but are connected with the same by cylinder passages 18 whichhave inner ports 18a sweeping the control ports 12 and 13.

In the embodiment of FIGS. 1, 3 and 5, the passages 18 are parallel tothe radial axes of the respective cylinders which intersect the rotoraxis A Assuming that the machine operates as a pump in the direction ofthe arrow 0, the axes of the cylinder passages 18 lead the axes of therespective cylinders 17.

In the embodiment illustrated in FIG. 2, the rotor passages 18' whichopen in ports on the inner surface llla' of rotor 11', are slanted tothe radial axes of the respective cylinders 15 so that the outer end ofeach rotor passage 18 is concentric with the bottom face 17 while thecylinder port 18' leads the radial axis of the respective cylinder 15 inthe same position as the cylinder ports 18a in the embodiment of FIG. 1.

When the machine is operated as a pump, rotor 11 or 11 is driven in thedirection of the arrow 0. After passing through the inner dead centerpoint Ti, the pistons 16 suck pressure medium through the low pressurecontrol portll3 and the cylinder passages 18 into the radial cylinders15, and displace the pressure medium, after passing through the outerdead center point Ta, into the high pressure control port 112. Betweenthe rotor 11, 11 and the control pintle 10, pressure areas develop dueto pressure medium leaking out of the control ports18a. The outwardlydirected forces of the pressure areas, compensate the inwardly directedforces acting on the rotor 11 due to the fact that in accordance withthe invention, the axial plane of symmetry E of the control ports 12 and13 is angularly displaced from the plane B, particularly when thecylinder ports 18a and 18a are displaced relative to the radial axes ofthe cylinders 15, as will now be explained with reference to FIGS. 3 to5.

FIG. 3 illustrates the embodiment of FIG. 1, but it will be understoodthat the diagram shown in FIG. 3 is also applicable to the embodiment ofFIG. 2.

Referring now to FIG. 3, in the angular regions a, and a which arebounded by the plane 13 and by a plane C perpendicular to plane B andintersecting the same in the rotor axis A at any time the same number ofpistons 16 is located due to the equal angular spacing of the axes ofcylinders 15. In the regions ,8, and B which are bounded by plane B andby plane D passing through the axis A; perpendicular to plane B, on theaverage, more pistons I6 are located in the region B; than in the region3 Since the inwardly acting mechanical forces P act alwaysperpendicularly to the inner cylin drical surface 14a of the actuatorring 14, the inwardly directed forces in the region 8 exceed on theaverage the inwardly directed forces B in the region [3,. Accordinglythe resultant P of the inwardly directed mechanical forces P in thepressure region is not perpendicular to the plane B, but definestherewith an angle less than 90 in the region of the inner dead centerpoint Ti.

FIG. 4 shows a radial piston pump according to the prior art with arotor 11' and high pressure and low pressure pressure ports 12' and 13'in the control pintle 10 which are arranged symmetrically to the plane Bwhich passes through the axes A and A In the machine of FIG. 4, theoutwardly directed forces of control pindle I acting on rotor 11" have aresultant P perpendicular to the plane B and passing through axis A,.Consequently, the outwardly directly resultant P of the arrangement ofthe prior art, cannot fully compensate the resultant P of the inwardlydirected mechanical forces, described with reference to FIG. 3.

In the arrangement of the present invention as shown in FIG. 5, thecontrol ports 12 and 13 are displaced in circumferential directionso-that the resultant vector P which passes through the axis A,, issubstantially parallel to the resultant P of the inwardly directedmechanical forces. Consequently, the two opposite resultant forces P andP fully compensate each other.

In order to prevent influencing of the timing of the flow into and outof the cylinder ports 180, the ports 18a are displaced relative to thecylinders 15. The control ports 12 and 13 are geometrically arranged onopposite sides of a second plane E which passes through the rotor axis Aat an angle to the plane B. The control ports 18a may be displacedrelative to the axis of the respective cylinders 15, the same angulardistance. The angle between the planes E and B may be the same as theangle between the plane D and the resultant force As compared with theprior art construction shown in FIG. 4, the high pressure control port12 is angularly displaced toward the inner dead center point Ti, whichis determined by the position of the actuator ring 14.

During operation as a pump, the rotor 11 rotates in the direction of thearrow 0 shown in FIG. 1. When the machine is to be used as a hydraulicmotor, fluid under high pressure is supplied through the control pintleto the high pressure port 12 which causes rotation of the rotor 11 inthe opposite counterclockwise direction.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofpiston pumps and hydraulic motors differing from the types describedabove.

While the invention has been illustrated and described as embodied in aforce compensating arrangement for a radial piston machine in whichcontrol ports and cylinder ports are angularly displaced as comparedwith the conventional arrangement, it is not intended to be limited tothe details shown, since various modifications and structural changesmay be made without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspexts of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

I claim:

1. Force compensating arrangement for a radial piston machine,comprising a control pintle having an outer cylindrical surface formedwith diametrically disposed circumferentially extending high pressureand low pressure control ports; a rotor having an inner cylindricalsurface mounted on said outer cylindrical surface for rotation about afirst axis, said rotor including equally angularly spaced cylindershaving radial cylinder axes intersecting said first axis and cylinderports on said inner cylindrical surface communicating with said controlports, and pistons in said cylinders; and an actuator ring surroundingsaid rotor and having an inner cylindrical actuator surface in slidingcontact with said pistons and having a second axis, said first and saidsecond axes being parallel and located in a first axial plane so thatsaid rotor has in said first plane inner and outer dead centerpointsclosest to, and farthest from, respectively, said actuator surfacewhereby a resultant of inwardly directed forces passes through saidsecond axis defining a predetermined angle less than with said firstplane in the region of said inner dead center point, said high pressureand low pressure control ports being symmetrical to a second planepassing through said first axis and defining such an angle with saidfirst plane so that the resultant of the outward directed pressureforces passing through said first axis is substantially parallel andequal to said resultant of said inward directed pressure forces forcompensating the same, said cylinder ports being circumferentiallydisplaced relative to said radial cylinder axes, respectively, an anglewhich is substantially equal to said angle between said first and secondplanes.

1. Force compensating arrangement for a radial piston machine,comprising a control pintle having an outer cylindrical surface formedwith diametrically disposed circumferentially extending high pressureand low pressure control ports; a rotor having an inner cylindricalsurface mounted on said outer cylindrical surface for rotation about afirst axis, said rotor including equally angularly spaced cylindershaving radial cylinder axes intersecting said first axis and cylinderports on said inner cylindrical surface communicating with said controlports, and pistons in said cylinders; and an actuator ring surroundingsaid rotor and having an inner cylindrical actuator surface in slidingcontact with said pistons and having a second axis, said first and saidsecond axes being parallel and located in a first axial plane so thatsaid rotor has in said first plane inner and outer dead center pointsclosest to, and farthest from, respectively, said actuator surfacewhereby a resultant of inwardly directed forces passes through saidsecond axis defining a predetermined angle less than 90* with said firstplane in the region of said inner dead center point, said high pressureand low pressure control ports being symmetrical to a second planepassing through said first axis and defining such an angle with saidfirst plane so that the resultant of the outward directed pressureforces passing through said first axis is substantially parallel andequal to said resultant of said inward directed pressure forces forcompensating the same, said cylinder ports being circumferentiallydisplaced relative to said radial cylinder axes, respectively, an anglewhich is substantially equal to said angle between said first and secondplanes.